碳网封装Fe3O4/还原氧化石墨烯锂离子电池负极材料

通过简单有效的溶剂热法将Fe3 O4颗粒与氧化石墨烯(GO)进行复合,得到Fe3 O4/GO复合材料.将Fe3 O4/GO与葡萄糖进行碾磨.在高温下将GO还原成还原氧化石墨烯(rGO)的同时在Fe3 O4/rGO表面制备网状结构的导电碳层,得到三维网络传输结构C/Fe3 O4/rGO复合材料.由碳网和还原氧化石墨烯组成...     

石墨烯修饰电极电化学阻抗法测量油脂的氧化诱导时间

分别采用滴涂法制备石墨烯(GR)-壳聚糖(CS)修饰玻碳电极(GR-CS/GCE),以及电沉积-还原氧化石墨烯(GO)修饰玻碳电极(rGO/GCE),并对修饰电极进行了电化学表征。结果表明,rGO/GCE比GR-CS/GCE及GCE有较小的电子转移阻抗和较大的表观活性面积。rGO/GCE电极的制备条件为GO悬浮液浓度1.0g/L、扫描速度20mV/s和电沉积30圈。优化了油脂阻抗测量条件,研究了油脂样品在rGO/GCE上的交流阻抗行为。根据rGO/GCE可以快速、准确地测量实际油脂样品(杏仁油)氧化过程中阻抗值及其变化,据此建立了一种简便、灵敏和准确测量油脂氧化诱导时间的电化学分析方法。     

基于石墨烯修饰电极的电化学生物传感

石墨烯是一种具有单原子厚度的二维碳纳米材料,具有大的比表面积、高的导电性和室温电子迁移率,以及优异的机械力学性能.石墨烯还具有电化学窗口宽,电化学稳定性好,电荷传递电阻小,电催化活性高和电子转移速率快等电化学特性.化学修饰石墨烯,特别是氧化石墨烯(GO)和还原氧化石墨烯(rGO),可以被宏量、廉价地制备出来.它们具有可加工性能,可以被组装、加工或复合成具有可控组成和微结构的宏观电极材料.因此,石墨烯及其化学修饰衍生物是用于电化学生物传感的独特而诱人的电极材料.例如,GO是一种化学修饰石墨烯,也是石墨烯的重要前驱体;其边缘具有大量的羧基可用于共价固定酶,从而能实现酶电极的生物检测.在GO上的不可逆蛋白吸附也可以促进蛋白质的直接电子转移以提高其电化学检测性能.但是,GO大量的含氧官能团破坏了石墨烯本征的共轭结构,降低了其电学性能并限制了其实际应用.GO可以通过化学、电化学、热还原等技术转化成rGO,从而能部分修复其共轭结构,提高其导电性与传感性能.另一方面,石墨烯是一种零带隙材料;原子掺杂可以调控其能带结构,提高其电催化性能.石墨烯材料也常常需要通过与其它功能材料的复合进一步改善其可分散与可加工性能,提高其电催化活性和电化学选择性.本文综述了本征石墨烯(包括GO,rGO和掺杂石墨烯)以及石墨烯与生物分子、高分子、离子液体、金属或金属氧化物纳米粒子等复合材料修饰电极在检测各种生物分子方面的研究进展,并对该研究领域进行了展望.     

氧化石墨烯片层大小对其修饰电极探测汞离子的影响

研究了石墨烯衍生物片层尺寸对Hg~(2+)检测的影响。通过超声制得片层大小不同的氧化石墨烯(GO),利用循环伏安法电化学还原得到相应的还原氧化石墨烯(rGO),然后利用循环伏安法研究了rGO/玻碳电极(GCE)和L-半胱氨酸(L-cys)/rGO/GCE两种修饰电极对于Hg~(2+)的响应,以及不同片层大小氧化石墨烯对应的rGO/GCE和L-cys/rGO/GCE修饰电极对于Hg2+响应的不同。     

氧化石墨烯浓度对还原氧化石墨烯/ZnS电化学性能的影响

以氧化石墨烯(GO)、乙酸锌(Zn(CH₃COO)₂)和硫脲为原料,采用水热法成功制备了还原氧化石墨烯/ZnS(rGO/ZnS)复合材料,并将该材料用作锂离子电池负极。高导电性的 rGO可以为锂离子和电子的传输提供有效的路径,ZnS可以提供较高的理论比容量。rGO/ZnS复合材料在rGO与纳米级高度分散的类球形ZnS颗粒协同作用下展现了较好的嵌锂容量和循环性能。当GO质量浓度为2 mg·mL^-1时制备的rGO/ZnS复合材料的倍率性能最好,循环稳定性最佳。     

石墨烯-ITO复合电极对聚苯胺薄膜电致变色性质的影响

采用改进的Hummers法制备氧化石墨烯(GO),首先,石墨与浓硫酸、过硫酸钾和五氧化二磷反应制得强氧化产物,随后将其与浓硫酸、硝酸钠、高锰酸钾反应,经双氧水发泡、酸洗、超声等合成氧化石墨烯水溶液,再通过金属箔还原和基底转移过程制备GO-氧化铟锡(ITO)复合电极材料.通过金属箔还原和基底转移过程制备GO-氧化铟锡(ITO)复合电极材料.利用电化学聚合法在GO-ITO复合电极上制备聚苯胺(PANI)薄膜,并对其形貌结构、电化学及电致变色性质进行表征.结果表明,与ITO电极相比,采用GO-ITO复合电极制备的PANI的成膜性得到明显改善,复合电极具有更加均匀细致的颗粒表面,增大了聚合物与电解液之间的接触面积,为电致变色过程中平衡离子的注入/脱出提供了更多的通道,因而PANI薄膜在700nm处的光学对比度提高了约13%,响应速度缩短了约2.6 s,着色效率高达169.6 cm2/C.GO的引入保持了PANI良好的电化学稳定性.GO-ITO复合电极有效改善了聚合物的综合性能,对于聚合物电致变色材料及器件的开发具有潜在的应用前景.     

还原氧化石墨烯表面聚苯胺纳米阵列的制备及电化学电容性能

本文以阳极氧化铝(AAO)膜为模板,通过恒电位法在自组装还原氧化石墨烯(rGO)膜表面制备有序聚苯胺(PANI)纳米线阵列。通过拉曼光谱和场发射扫描电子显微镜分别对其结构和微观形貌进行了表征,并对PANI纳米线阵列的电化学电容性能进行了测试。结果表明,rGO膜表面可电沉积PANI,电沉积得到的PANI纳米线阵列具有比PANI薄膜材料更高的电容和比电容。     

石墨烯氧化物薄膜电极的光电化学特性

采用浸渍-提拉法制备了一系列石墨烯氧化物(GO)薄膜,并通过X射线衍射(XRD),扫描电镜(SEM),傅里叶变换红外光谱,紫外-可见吸收光谱和光电化学测量等技术对样品进行了表征.在GO电极上观察到阴极光电流,且光电流密度受薄膜的厚度影响.GO薄膜电极厚度为27nm时,光电流密度为0.25μA·cm-2.此外,GO电极的光电响应还受紫外光照影响,随着紫外光照时间的延长,阴极光电流逐渐减小.该工作提供了简便的通过控制薄膜厚度或紫外光照时间来控制GO薄膜半导体光电化学性能的方法.     

石墨烯修饰Y型TiO_2纳米管光电极制备及其对氨氮催化氧化性能

采用三步阳极氧化法和一步循环伏安电沉积法制备了还原氧化石墨烯(rGO)修饰的Y型TiO_2纳米管(rGO/Y-TiO_2NTs)电极。通过场发射电子扫描显微镜(FESEM)、X射线能谱(EDS)、X射线衍射(XRD)、紫外可见漫反射光谱(UV-Vis DRS)及拉曼光谱(Raman)等对电极样品进行了表征。以rGO/Y-TiO_2NTs电极为光阳极,测试了不同循环伏安沉积圈数对电极光电流响应的影响,考察了在1.0 V偏压下电极对氨氮的光电催化氧化性能。结果表明,高度有序的Y-TiO_2NTs为锐钛矿型,具有大的比表面积,表面修饰平滑透明rGO薄膜后可显著提高其光电催化效率,沉积圈数为30时电极在30 min内对氨氮的光电催化氧化效率为95.9%。     

二氧化锰/石墨烯/N-取代羧基聚苯胺复合修饰电极对亚硝酸根的电化学催化研究

采用电聚合、静电吸附和恒电位还原的方法在玻碳电极上制备了均匀修饰的还原氧化石墨烯/N-取代羧酸聚苯胺(rGO/NPAN)复合膜。以其为支撑,利用滴涂法将高电催化活性的二氧化锰负载于复合膜上,形成MnO_2/rGO/NPAN复合修饰电极。通过扫描电镜(SEM)对复合膜的形貌进行表征,讨论了NPAN电聚合圈数、GO浓度、电还原时间和pH值等因素对电化学活性和电催化活性的影响。结果表明:该修饰电极具有低的检测电位和高的电化学响应,检测亚硝酸根的浓度范围为0.5×10~(-6)~5.13×10~(-2)mol/L,灵敏度为14.075μA·(mmol/L)~(-1),检出限(S/N=3)低至0.2μmol/L。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.